Frame Rate (FR) is a term used in the video industry to indicate how many images (or frames) are displayed per second. The FR is independent of and different from the resolution of the images.
Produced Content refers to content that has been edited and/or assembled from raw video captures into a digital data stream. The editing may occur “real time” as in the example of a football game being filmed with multiple cameras around a stadium, then assembled in real time with the audience viewing the Produced Content. The sources edited or assembled can include recorded sports action, commercials, interviews, etc. Another example is the editing of a cinema movie where various scenes are filmed across many months, then brought together, edited and then post processed into a final Produced Content.
The Society of Motion Picture and Television Engineers (SMPTE) is a consortium of professionals in the video field that create and maintain standards by which various video formats are created, encoded, transported and stored. Formatting of Ancillary (ANC) video information is covered in standard 291M. In the standard, ANC video information can be transmitted within the video data.
Traditionally, cinema camera frame rates captured data at 24 frames per second (fps). Advances in technology have enabled higher frame rates, such as without limitation 48, 60, 96 and 120 fps to suit specific content. Future systems are expected to produce higher frame rates such as 240 and 300 fps. Higher frame rates are used to capture quick moving events and make for a higher quality viewing experience because quick movement in the video Produced Content appear smoother and with less blur to the viewer (when compared to video produced at slower frame rates).
The use of higher frame rates comes at a cost of larger data storage size and higher bandwidth for transmission. For that reason, it is desirable to only use the higher frame rates where the content dictates it, reverting back to lower frame rates where appropriate. Content of this type is called variable frame rate (VFR) and the capability of producing it exists.
However, as currently implemented, the ability to directly display variable frame rate content in a display system without visual artifacts due to the rate changes does not exist. In prior known systems, visible artifacts are created when the frame rate dynamically changes because of the time duration it takes for the display device to comprehend the new frame rate, synchronize to the new data arrival rate and then finally begin to correctly produce the image. This problem is equally applicable to motion pictures, television, web, or any display of produced video content.
In cases where displaying variable frame rate video content is desired, one prior known approach is to mask the visible artifacts caused by frame rate transitions from view by inserting dummy or black frames into the video stream so that the artifacts are less likely to be visible to the viewer while the display re-synchronizes to the new frame rate. The dummy or black frames presented to the viewer may be noticed, making use of this approach undesirable especially in cinema and sports applications.
In another case, an additional processor may be employed within the video display to convert variable frame rate data into a single frame rate data. The additional processor approach has drawbacks as well. In addition to the extra cost, the conversion necessitates some interpolation of the video frames which the viewer may notice and the displayed images may differ from the original content. The original producer of the Produced Content has no control over the way the video is displayed by the system in these known approaches.
FIG. 1 depicts a block diagram of a conventional video display system. In FIG. 1, in system 100, digital video data 110 is provided to a digital video display system 120. Within the digital video display system 120, the digital video data 110 is received by video processing logic 130. Part of the video processing logic 130 is a frame rate detection block 122. The frame rate detection block 122 is coupled to a processor 128. The processor 128 has access to data used for proper timing by the Display Hardware 140 and updates this data in registers or by other means indicated by a Timing Configuration Buffer (TCB) 124. In operation, the video processing block 130 receives digital video data 110 and stores the image data into a frame buffer 126. The frame rate detection block 122 updates the processor 128 with the frame rate. The processor 128 updates parameters in the TCB 124 which enables the display hardware 140 to display the frames of digital video data 110 with the correct timing. In a typical system, when the frame rate changes, it may take many frames for the parameters in the TCB 124 to be fully updated. During that period, the system may produce visual artifacts which the viewer can deem undesirable. The visual artifacts result from displaying video images using an incorrect frame rate.
The prior known solutions cannot directly display variable frame rate video data without visible artifacts in the displayed image. Improvements in the direct display of video Produced Content including variable frame rates are therefore needed in order to address the deficiencies and the disadvantages of the prior known approaches. Solutions are needed that allow direct display of the VFR video content which eliminate or reduce the visual artifacts that exist in prior known solutions.